Often fluids need to be removed from wells, either to recover a useful fluid such as oil or water or to remove an unwanted fluid such as water in a gas well. Of particular difficulty is the removal of produced water from a gas well when the formation pressure begins to decrease and the well begins to produce increasing quantities of water. At some point a water column will form in the well and block the flow of gas. The water must then be removed to restore gas flow. Foaming agents may be injected into the well to reduce the water density and assist the gas flow in carrying the foam, and hence the water, out of the well. However, if the gas flow has ceased, the water must be removed to restart the gas flow.
Gas wells are typically deep wells, in the range of 8,000 feet to 20,000 feet deep, and often have small diameters, of the order of four-inch casings having inside diameters of about three inches. These characteristics make it difficult to remove water using conventional pumping systems. Water is commonly lifted from such wells using large volumes of nitrogen gas to carry water droplets out of the well, and preventative measures, such as foaming agent injection, are used to retard shutoff of the gas flow by the water. However, production time is lost whenever a nitrogen lift procedure is done, since the well must be flared for a period of time to reduce the nitrogen concentrations to insignificant levels. Typical costs for a nitrogen lift operation are approximately $20,000 for a single nitrogen lift operation, $20 per day for injection of a foaming agent, and $7,000 for lost production for a 350 mcf per day well. Further, a nitrogen lift might be required every 1 to 2 months for a well that is producing 20 to 40 gallons of water per day. Total costs for maintaining gas well production may exceed $150,000 annually. As stated, small well bores make the use of conventional plunger pumps and electric motor driven pumps to remove the water difficult, if not impossible. Jet pumps can be and are being used, but these pumps require dual, concentric tubing systems. Dual, concentric tubing is considerably more expensive than single tubing. It has a larger diameter, which restricts the well bore, as well as requiring more complex and expensive equipment for installation and operation than would be required for use of a single tube.